Extraction of Azo Dyes from Aqueous Solutions with Room Temperature Ionic Liquids.

In this work, ionic liquids/water distribution ratios (D) of azo dyes, including 1-(phenylazo)-2-naphthol, 1-(2-pyridylazo)-2-naphthol, 4-(nitrophenylazo)resorcinol, 4-(2-pyridylazo) resorcinol, and 2-(4-dimethylaminophenylazo) benzoic acid, have been determined experimentally. It was found that the D values are highly influenced by the pH of the water phase and the type of salts added. They increase with increasing alkyl chain length on the cations of the ionic liquids, and the anionic effect follows the order [BF4]- > [PF6]-. Possible extraction mechanism and selective separation of some azo dyes are also investigated. The results suggest that ionic liquids have potential applications in the removal and selective separation of azo dyes from water. [ABSTRACT FROM AUTHOR]